The invention refers to a weaving machine of the so-called progressive shedding loom type, wherein a series of disadvantages of known such machines have been overcome by the provision of the following features:
A. Improved driving of the devices which insert and beat-up the weft threads between the warp threads, such devices hereinafter being referred to as "inserters".
B. The system of feeding the weft threads to the inserters, which in turn subsequently introduce the weft threads into the shed, is improved.
C. The heald actuating system which opens and closes the warp threads to allow passage of the inserters and which crosses the warp threads behind each inserter after the deposit thereby of a new weft thread, is improved.
However, before explaining in detail the characteristics of the invention which advantageously eliminate the disadvantages of known machines, and also before referring in detail to the different embodiments of the invention, in view of which even a dual weaving machine can be constructed which is capable of simultaneously producing two lengths of fabric with a minimum of additional elements, a brief explanation will be made of the characteristics as well as of the disadvantages of known machines of this type.
Presently known weaving machines of the progressive shed type are mainly constructed from a warp thread feeding roller and a roller which collects the fabric produced, such rollers being superposed and between which there is a shed tunnel wherein the warp threads are controlled by a plurality of healds which are positioned within planes which are perpendicular to the vertical planes occupied by the shafts of the rollers, and which are alternately linearly moved in directions which are also perpendicular to the planes occupied by the roller shafts.
The healds are mere elongated elements which have an opening through which the warp thread passes and which are connected in groups, each group being composed of at least two healds. The healds are superposed within each group, and comprised within the same perpendicular plane as those occupied by the shafts of the rollers.
The planes which define the position in space of each group of healds are therefore parallel to each other.
The warp threads, furthermore, after passing the corresponding healds, are driven very close to each other between two guide elements which force the warp threads to be joined from such moment onward until the fabric collecting roller is reached, whereat when operation starts the warp threads should be fixed.
The healds receive alternate opposed lineal movements within each group, so that the threads being controlled thereby are open or separated each time the healds which are driven in opposite directions away from each other, and so that the threads are subsequently crossed when the healds receive reversed movement. Before the healds are moved to opposite extreme positions, they are exactly superposed.
As can be appreciated from the fact that the warp threads are guided together after their passage through the healds, the separation and crossing of the threads, as produced by the healds, is effected from the point where the guide means force the threads to be held together.
Immediately on top of the guide means, which force the threads to be joined after being controlled by the healds, and moving within a path between such guide means and the healds, there are a plurality of inserters which are spaced from each other at short, regular intervals and which are synchronously moved. Each one of such inserters deposits a weft thread between the warp threads which, in view of the above mentioned arrangement, are separated in front of each inserter and cross behind the same, on top of the weft thread deposited thereby. Each inserter, at the same time as it deposits a weft thread, beats up the weft thread deposited by the preceding inserter, pressing the cross of warp threads thereon.
The shed tunnel is formed by the grouping of various warp threads controlled by the healds. Such shed is open when the warp threads are separated, thus permitting the passage of the weft inserter, and it is closed when the warp threads are crossed on top of the weft which has just been deposited.
Since there is, at each given moment considered, within the shed tunnel a plurality of weft inserters, of which that which is just entering the shed has all of the weft thread thereof, while that inserter which is leaving the shed has already exhausted the weft thread thereof, having deposited the same between the warp threads, and the remaining inserters have different amounts of their respective weft threads, it is clear that the groups of healds cannot act synchronously. That is, the healds cannot be displaced half towards one side and the other half towards the other side, since when the threads handled thereby are crossed, they would butt against the inserters which are interposed in their path. Consequently, the healds are progressively actuated, in a snake-shaped path, from the beginning of the shed tunnel, with the result that some groups are separated in front of the inserters while others are closed from behind, all of which takes place continuously and progressively.
In the above mentioned types of looms, the weft thread inserters are actuated by electrical or mechanical devices.
In the electrical type looms, driving is carried out by means of electromagnets functioning inside the shed, each one of which actuates a weft thread inserter element.
This system has two main inconveniences. The first relates to the weight of the electromagnets and their brackets, which results in a great inertia, reducing the speed of the machine and increasing the time necessary for braking. The other inconvenience is that, owing to the fact that the warp threads must be placed between the electro-magnet and the inserter device, they must bear the pressure between such two elements, which causes friction capable of damaging the warp thread.
In known mechanical systems, adjustment of beating up of the weft thread between inserters is effected by the individual advance of the teeth of the reed. These movements of the teeth of the reed are, in the majority of known systems, used to displace the inserters within the shed. One of the biggest problems of such systems, from the textile point of view, is that the individual movement of the teeth of the reed results in a change in density per warp of the fabric being produced, as a result of the play and wear on the teeth. Another important difficulty involves changing the density per warp of the fabric, since in order to achieve such change it is necessary to change all the elements forming the reed. Furthermore, from a mechanical point of view, serious drawbacks are caused by wear of the teeth of the reed through friction with the inserters, as well as the fact that the teeth of the reed must effect a long run or travel in order to achieve beating up of the weft thread. This is a limitation on the speed of the machine.
Furthermore, in known looms of the progressive shed type, there are various ways of feeding the weft to the inserters. However, all such known feeding systems have drawbacks which mainly reside in the fact that various inserters operate simultaneously within the shed. As a result, the inserters must be filled one after the other. Thus, the displacing movement of the weft thread is much higher when the bobbins of the inserters are to be filled than when the weft thread is to be inserted in the sheds.
A known weft feeding system uses a suction effect which draws the weft thread towards the interior of the tank with which each inserter is equipped. Thus, the thread is not wound on any bobbin whatsoever. This system has the inconvenience that the weft thread is not methodically placed within the inserter, and furthermore, when the thread is deposited in the sheds, it undergoes tension irregularities which produce defects in the fabric being produced. Another inconvenience is that derived from the speed to which the weft thread should be subjected during filling of the inserter. This makes measurement thereof difficult, and consequently makes difficult the achievement of an arrangement such that the threads stored in each of the inserters are the same and equivalent to the width of the fabric being manufactured. A further difficulty is due to the fact that since the inserters should operate one at a time at the feeding site, they have very little time in which to effect a thread loading operation. Thus, the feed mechanisms are very delicate, expensive and of short duration. Furthermore, in the inserter feed system under discussion, high quality threads should be used, since these threads are subjected to high tensions when pushed with a force which is sufficient in order to reach the high displacement speeds which are necessary.